The present invention relates to systems for utilizing energy from fossil fuels, and particularly systems of this type equipped to undergo periodic removal of soot deposits.
Typical systems of this type are boilers which are fueled by coal or oil and which produce steam for driving the turbines of an electrical power generating plant. Typical boilers include, among other components, a furnace evaporator section and various heat exchange units such as superheaters, reheaters, economizers and, possibly, air heater sections. A furnace evaporator section is provided with water walls, while the various heat exchange units include tubing carrying the medium, in the form of water or steam, being heated, while combustion gases flow past the water walls and over the tubing.
Despite all efforts to optimize the fuel burning process, all combustion gases contain a certain amount of solid and/or molten products, including ash and soot which form deposits on the water walls and tubing surfaces.
These deposits interfere with the transfer of heat energy from the combustion gases to the medium being heated. Moreover, if these deposits are permitted to form a layer of a certain thickness, the outer surface of such layer may reach a temperature at which constituents thereof become sintered or molten, resulting in deposits which grow rapidly, resist removal, create partial or total blockages in the gas flow paths of the boiler, result in heavy accumulations which may fall and hence cause mechanical damage within the boiler, and cause corrosion damage due to diffusion of molten or vapor materials into the tubing surfaces.
In order to prevent such problems from occurring, it is known to equip such a boiler with soot blowers, which may be fixed, rotating and/or retractable, and which are activated periodically to direct jets of steam, air and/or water onto the surfaces where deposits form in order to effect removal of such deposits from the boiler. It is known to equip such blowers with control devices which direct the blowing nozzles toward the surfaces to be cleaned and activate the flow of the blowing medium at appropriate times. Such control devices may operate soot blowers individually or in groups on command by a boiler operator and/or according to a predetermined time pattern.
Each soot blowing operation itself involves a certain cost and current soot blowing practice does not take account of all of the costs involved in a manner to seek to optimize the economic benefits of soot blowing.